Oars (or paddles) are used to propel watercraft, such as pleasure craft, working boats and racing boats. Oars are devices for converting the efforts of an oarsman into the propulsion of the craft through the water. For the sake of clarity, oars, paddles and any other similar manually operated water propulsion devices are all referred to as “oars” or “oar” in this document.
An oar may typically consist of a blade, a handle which the oarsman holds, and a shaft which connects the handle to the blade. The blade may be shaped like a flattened spoon and the front surface of the blade exerts pressure on the water when the handle is pulled.
The shaft and blade combined are normally substantially longer than the handle. The shaft can rest in a rotating pivot called a rowlock which is attached to the side of the boat. This pivot converts the oar into a lever. The force exerted by the oar on the water may be passed to the boat through the rowlock, causing the boat to accelerate in the opposite direction to the movement of the blade. However, rowlocks are not essential and the boat can be propelled without one, as in the case of a canoe.
Oar designs have changed little since the oars used by the ancient Greeks to power vessels such as triremes 3000 years ago. New materials have been used to make them lighter and stronger, the oar shape has been modified somewhat but otherwise they are substantially the same. In the sport of rowing the shape of the blade has evolved in recent years to make it broader and longer so that it can act on a bigger area of water. This makes the boat go faster but also requires more strength to move the oar through the water.
In competitive rowing, there is always a need for improved designs which make oars more efficient in order to make the boat go much faster for the same effort.